The author of this sentence is Liu Xiang, an official, bibliographer and writer of the Western Han Dynasty. The specific source cannot be verified, and some of them are from Liu Xiang's Shuo Yuan.

It means that a good secretary is like medicine. Books can cure people's ignorance if you can make good use of them and study hard.

Liu Xiang and Liu Xin and his son are important figures who re-studied and sorted out hundreds of books and theories after Confucianism was unified into Confucian classics, and stressed that they should learn from them to improve Confucianism. He said this not only because of the great role of books, but also because of his experience in sorting and compiling.

Extended data:

Liu Xiang, whose original name is Gengsheng and Liu, is a descendant of Liu Bang's half-brother and Liu Xin's father.

His prose is mainly related to Gao's ancient books, among which the famous ones are Jian Ying Chang Ling Shu and Zhang Guo Ce Shu, which are characterized by simple narration, fluent theory and ease.

I was ordered to lead the school secretary and wrote Bielu, the earliest open book catalogue in China. Today, there are books such as New Preface, Shuoyuan, Biography of Lienv, Warring States Policy, Biography of Liexian, etc. His book The Five Classics and Yi Tong was compiled by Ma Guohan of A Qing Dynasty. The Songs of Chu was compiled by Liu Xiang, and The Classic of Mountains and Seas was compiled by Liu Xiang and his son Liu Xin.

References:

Baidu Encyclopedia-Books or Medicine?